Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
List = [input() for i in range(H)]
queue = [(0,0,1)]
shape = sum(row.count("#") for row in List)
used = {(0,0)}

def check(x,y,c):
    if x > W-1 or y > H-1 or x < 0 or y < 0:
        return
    if List[y][x] == '#':
        return
    if (x,y) in used:
        return
    queue.append((x,y,c))
    used.add((x,y))
    
f = -1
while queue:
    x,y,c = queue.pop(0)
    if x == W-1 and y == H-1:
        f = 1
        break
    check(x+1, y, c+1)
    check(x,y+1,c+1)
    check(x-1,y,c+1)
    check(x,y-1,c+1)
print(f if f == -1 else(H*W - c - shape))